1. Field of the Invention
The invention relates to methods and apparatus for the manufacture of a combustible gas, principally methane. More particularly, it is concerned with the utilization of organic wastes such as grass clippings, leaves, sewage sludge, etc. as a source material for the production of a combustible gas, principally methane. The residue, swept from the bottom of the vessel by a moving current of water, may be recovered for use as fertilizer if desired.
2. Description of the Prior Art
The production of methane gas by bacterial decomposition of organic materials is well known. The accumulation of methane over swampy areas has been observed for at least 100 years. More recently the accumulation of methane in the vicinity of trash landfilled areas has been noted with some concern.
Millions of pounds of organic waste and trash are generated daily in the United States. Up to the present time the method of disposal of these materials has been in the so-called sanitary landfills. It has been recognized from time to time that the disposal of such wastes is a potential source of valuable energy and that thus energy could be recovered in the form of a combustible gas principally methane, with minor amounts of carbon monoxide, carbon dioxide and hydrogen, by the bacterial decomposition of this organic waste in a controlled manner.
There are several patents that disclose the pyrolysis of organic wastes to recover various gas and hydrocarbon fractions. U.S. Pat. No. 3,852,048 relating to a process for the production of industrial fuels from waste woody materials and U.S. Pat. No. 1,383,888 relating to a process for carbonizing wood and other carbonaceous materials are representative of the art in this area.
Although the pyrolysis systems produce a satisfactory product, they require the use of a substantial amount of heat which tends to reduce the economic value of the systems.